1. Field of the Invention
The present invention relates to a method for producing an integrated magnetic head structure. More particularly, it relates to a method for definitively fixing the breadth of the magnetic layers in the vicinity of the end face to determine the track breadth of an originally broader magnetic layer structure of magnetic and non-magnetic, insulating and electrically conductive layers by ion bombardment.
2. Description of the Prior Art
A method of the type generally set forth above is disclosed in U.S. Pat. No. 4,016,601. Initially, the magnetic layers of an integrated magnetic head structure are also made wider in the region of the subsequent end plane than is necessary for the desired track breadth. Consequently, it is necessary to reduce the breadth of the magnetic layers at this point in a further operation, which operation must be carried out with great precision since mechanical access to the recording tracks must be more and more precise. In addition, to obtain optimum electro-magnetic efficiency it is important to keep the magnetic layers as broad as possible at the points at which they cover the stack of conductive layers for the formation of the magnetic head winding. Moreover, it is very difficult to produce structures that are only 20 .mu.m or less in breadth by application of the corresponding materials by vapor deposition or sputtering with the aid of perforate masks and obtain sufficient precision.
For a better understanding of the prior art process, reference is made to FIG. 1 which is a diagrammatic illustration of an integrated magnetic head structure which comprises a large number of thin layers. The magnetic head winding 1 comprises electrically conductive and insulating layers, in alternation, together with the terminal connections 2 and is not of particular importance with respect to the invention. The magnetic layers which form the pole piece 3 and an invisible pole piece 4 disposed beneath the pole piece 3 and extending through beneath a magnetic head winding 1 are initially produced with a breadth L as far as the subsequent end plane 5 and continuing beyond that plane. It is only in a further operation that the breadth of the magnetic layers in the vicinity of the end plane 5 facing the recording carrier when in operation, i.e. the gap breadth, is reduced to the value l. In this connection, the known procedure is to fine-machine (polish) the end plane including the substrate, cover those zones that are not suppose to be worn down, by fitting a mask to the end plane, and bombarding the end plane with ions at right angles thereto. In this manner, the predetermined gap height should be maintained at least roughly to a distance T of at least 5 .mu.m from the end plane.
The ionic bombardment causes the zones struck by the greatly accelerated ions to heat up a great deal. In order to avoid overheating of the sensitive magnetic layers, the magnetic head structure could be cooled during processing by placing the substrate on a water-cooled plate having excellent heat conduction properties. But this technique produces difficulties when the ion bombardment is carried out at right angles to the end face. Another problem arises in that the layers forming the pole pieces wear down at different rates. As a result, the magnetic layers and the insulating layers lying therebetween are worn down to different depths.